Contents Introduction § 0. Definitions, notation, and basic facts § 1. The universal 1-form. Lagrangian manifolds § 2. Fields and 1-forms on Φ § 3. Poisson brackets § 4. Symmetries § 5. The structure of Hamiltonian systems with a given degree of symmetry § 6. Completely integrable systems § 7. The theorems of Darboux and Weinstein § 8. Invariant Hamilton-Jacobi theory § 9. Hamiltonians of mechanical type § 10. Mechanical systems. Examples Appendix I. Bifurcations Appendix II. A. V. Bocharov and A. M. Vinogradov, The Hamiltonian form of mechanics with friction, non-holonomic mechanics, invariant mechanics, the theory of refraction and impact References